放牧对短花针茅荒漠草原植物多样性的影响

摘要

Grassland plant diversity is a core issue in grazing ecology.We examined the effects of grazing intensity on plant diversity across four levels of organization (plant individual,species,functional group,and community) in Stipa breviflora desert grassland using a six-year sheep grazing experiment in Sonid Right Banner,Xilingol,Inner Mongolia Autonomous Region of China.Species richness was greater in the no-grazing plot than in the moderate-and heavy-grazing plots.The differences were due to two functional groups,perennial forbs and annual forbs.The relative weight of each functional group was not affected by grazing intensity.At the community scale,grazing intensity did not significantly affect richness.However,the Simpson ecological dominance index,Shannon-Wiener diversity index,and Pielou evenness index of nograzing plot plant communities were greater than those of the moderate-grazing plot and significantly greater than those of the heavy-grazing plot (P＜0.05).At the functional group scale,the diversity indices of perennial grasses and annual herbs had no significant responses to grazing.The diversity index of no-grazing plot plants was greater than those of moderate-and heavy-grazing plots;the moderate-grazing plot diversity index was higher than that of the heavy-grazing plot.Stipa breviflora desert grassland communities were all unstable to some degree,but the moderate-grazing plot stability was greater than those of the no-and heavy-grazing plots.Our research suggests that an increase in grazing intensity will decrease plant diversity at multiple levels of organization in Stipa breviflora desert grasslands.However,moderate-grazing grasslands were relatively stable.Therefore,the balance of plant diversity and stability will be an important way for developing the regional scientific grazing intensity.%放牧干扰对草原植物多样性影响机制是放牧生态学研究的核心问题.以内蒙古锡林郭勒盟苏尼特右旗的短花针茅荒漠草原的长期放牧控制实验为平台,系统研究了放牧调控下植物多样性随组织尺度转换的影响,为荒漠草原植物多样性尺度推绎提供理论基础.结果显示:1)现存草地物种数未放牧最高,适度放牧次之,重度放牧最低,差异体现在多年生杂类草和一年生草本2个功能群上,且各功能群的权重基本不受放牧强度影响;2)群落尺度,放牧强度没有显著影响丰富度指数,未放牧小区的植物Simpson生态优势度指数、Shannon-Wiener物种多样性指数与Pielou均匀度指数大于适度放牧小区,显著大于重度放牧小区(P＜0.05);功能群尺度,多年生禾草与一年生草本的多样性指数对放牧无显著响应,多年生杂类草的多样性指数未放牧小区最高,适度放牧小区次之.3)Godron群落稳定性指数显示,适度放牧的小区稳定性高于未放牧小区和重度放牧小区.研究表明,放牧强度的上升使短花针茅荒漠草原不同组织尺度植物多样性降低,但群落稳定性结果显示适度放牧的草地表现出了更高的稳定性,植物多样性与稳定性的权衡将是合理制定区域科学放牧强度的重要途径.